Document "preRegisterDynamicContracts"

[PaulRBerg]

Mentioned here https://medium.com/@envio_indexer/envio-developer-update-october-2024-8a3706d3e038 but nowhere to be found in the docs

[DZakh]

It's removed in the latest version, since we made default mode faster. There is a one liner in the docs, saying that it's deprecated.

[moose-code]

Closed in #642